His government had lobbied for a stay of execution while the case was considered, hoping the United States Supreme Court would issue a stay of execution. The high court reconsidered then rejected a stay Wednesday.

In condemning the execution by lethal injection, the Mexican leader was referring to a ruling by the United Nations International Court of Justice at The Hague.

In 2004 the court ruled that United States had failed to inform 51 Mexican nationals on death row in the U.S. at the time — including Tamayo — that they had a right to consular assistance.

Tamayo was convicted of shooting a police officer in Houston in 1994 by firing three bullets into the officer’s head. Tamayo was in the U.S. illegally and had a criminal record in California where he had served time for robbery and was paroled.

In the past five years, Texas has executed two other Mexicans convicted of murder who raised similar claims. The Supreme Court refused to delay either of those executions, which took place in 2008 and 2011.

The U.S. State Department has said the execution will make it more difficult to provide consular assistance to U.S. citizens facing criminal charges abroad.

The State Department released a statement on Thursday saying it "regrets Texas' decision to proceed with Mr. Tamayo's execution without that review and reconsideration, but remains committed to working to uphold our international obligations.”

“It doesn’t matter where you’re from,” said Lucy Nashed, the spokesperson for Gov. Rick Perry. “If you commit a despicable crime like this in Texas, you are subject to our state laws, including a fair trial by jury and the ultimate penalty.”

Texas argued that it is not bound by the ruling of the International Court of Justice.